Apparatus for producing bellows folds in tubing



Sept. 19, 1950 J. E. wooDs 2,522,915

APPARATUS FOR PRODUCING BELLOWS FOLDS IN TUBING Filed Nov. 8, 1946 EL [CTR/C POWER .SUPPLY Patented Sept. 19, 1950 APPARATUS Fon raonncnvo BELLoWs Fotos 1N TUBING John E. Woods, Cohasse mesne assignments, to S poration, Bolton, ware t, Mass., tandard-Thomson Cor- Mass., a corporation of Delaassignor, by

Application November 8, 1948, Serial No. 708,674

8 Claims.

The present invention relates to apparatus for producing bellows folds in tubing and is particularly concerned with apparatus of the type described in the Clifford Patents No. 1,689,620 and 1,823,532 dated October 30, 1928, and September 15, 1931, respectively.

According to the disclosures in the above mentioned patents, a tube is placed within a series of accurately spaced separable die plates. A bulging pressure is then applied internally to the tube whereby the tube is bulged in the spaces between the plates. The spacing means are then removed and the tube is subjected to a lengthwise contracting pressure while maintaining fluid pressure within the tube. The fluid pressure maintained within the tube during the contracting operation supports the tube walls and causes the bellows folds to be formed without creasing or wrinkling of the metal.

The characteristics of the finished bellows are dependent upon the characteristics of the tube and also upon the extent of the initial bulging operation. For any given bellows, it has been customary to bulge at a determined pressure. This is satisfactory whenever the tubes are substantially uniform. However, the tubes frequently vary not only in dimensions but also in their physical properties. Accordingly, a number of bellows made under identical pressure conditions will exhibit variations in outside diameter and in flexibility because of the unavoidable variations in the original tubes.

I have discovered that one of the major factors in the non-uniformity of the finished bellows arises from the variations in the amount of bulge, and that if the bulge is always brought to a predetermined size the resulting bellows will exhibit greater uniformity in their characteristics in spite of unavoidable variations in the characteristics of the original tubes. For example, a tube which is thinner than normal will, under normal practice, bulge to a greater diameter. Under the subsequent contracting operation, the folds will be carried out to a greater diameter than normal, the wall thickness will be reduced, and the flexibility will be increased. Conversely, a tube which is thicker than normal will result in a bellows of smaller outside diameter and less flexibility because it does not bulge to the required degree under the fixed bulging pressure.

According to the present invention, the amount of bulge is determined dimensionally, and the bulging pressure is v'aried in dependence on the tube characteristics.

According to the preferred form f the invens the plates I6 are accurately spaced by uring device 22 is provided.

tion a measuring device `is provided, which upon bulging of the tube to a predetermined diameter, acts to seal within the bellows the pressure at which that predetermined diameter was reached. Thereafter, the pressure is maintained during the contracting operation. Therefore, the internal pressure during contraction is gauged to the tube characteristics since these characteristics determine the extent of the bulge. Uniformity of the product is thus promoted by the fact that a thin tube is both bulged and contracted under a. lower internal pressure than a thick tube. The resulting bellows show markedly smaller variations in outside diameter and flexibility than bellows formed under a uniform bulging pressure.

In the accompanying drawings Fig. 1 is a diagram of the preferred apparatus for practicing the invention and Fig. 2 is a section on line 2-2 of Fig. 1 showing the measuring means.

The apparatus shown in Fig. l comprises a head 4 having a passage 6 through which iluid is admitted to the interior of the tube and a ram 8 which is moved to the left for contracting the tube. A tube I0 is supported in fluid-tight relationship between the head 4 and the ram 8. As shown in the drawing the tube has an integral base portion I2 seated against the ram and a flange portion I4 to engage the head.

Surrounding the tube is a set of separable die plates I6 uniformly spaced along the tube and in engagement with the wall thereof. Initially means of spacers I1. The frame of the machine, the mounting of the head and ram, and the form and number of the die plates are not shown in detail since these parts are described in sufcient detail in the Clifford patents above referred to. Moreover, for simplicity of illustration, only a short tube is shown and the length and diameter of the bulges are considerably exaggerated.

Fluid pressure is supplied to the tube from a suitable source indicated diagrammatically as a piston pump I8 connected to the water passage 6 by a pipe 20. Upon application of pressure from the source at I8 the tube is caused to bulge as indicated in Fig. l, after which the ram is moved to the left for the contracting operation. The source I8 is capable of developing a pressure in excess of that required for operation of the system. As the pressure increases, the bulge increases and the invention has means for isolating the tube from the pressure source when the bulge reaches a certain amount. To this end, a meas- This is in the form amavisV of a caliper inserted into the space between two adjacent plates I8 during the bulging operation. The caliper comprises a yoke 24 attached by a suitable bracket to the spacers l1. The yoke carries at one side an adjustable pin 28 and at the other side a microswitch 23. The switch is provided with wires 80 connected between an electric power supply and a solenoid valve 32 in the line 20. When the tube bulges sufilciently to close the microswitch contacts, a circuit is completed to operate the valve to shut olf the connection between the source I8 and the tube. As described in the above-mentioned patents, the spacers i1 are removed from engagement with the plates, in readiness for the tube collapsing operation. The caliper, being mounted on one of the spacers. is withdrawn at this time. It will be understood that the valve 32 should remain closed after the caliper is withdrawn, and this may be accomplished by using a valve 32 of thel reset type which remains closed until reset, as by the lever 34. The bulging pressure is thus retained within the tube.

The ram 8 is then moved to the left in a manner fully described in the above-mentioned patents, to collapse or contract the tube longitudinally to form the bellows folds. The walls of the tube, being supported by the internal pressure, fold outwardly between the die plates. The plates float unrestrained except for their interlocking relation with vthe tube during the contracting operation. During the iirst part of this contracting operation the volume increases and thereafter it decreases. A pressure equalizing device is provided to maintain the pressure at a proper value during the entire contracting operation. The equalizing device as shown in the drawing preferably comprises an accumulator 36 consisting of a tank having an internal rubber bag 38 filled with air under pressure. If the accumulator is of suflcient size, a substantially constant pressure is maintained during the collapsing operation. At completion of the collapsing operation, the bellows is fully formed.A The machine may then be opened to permit removal of the bellows. In order` to conserve the pressure of the liquid in the accumulator, a valve l0, here shown as a manually operated valve, is placed between the accumulator and the forming machine, and this valve is closed prior to opening the machine for removal of the bellows.

It will be observed that the measuring device 22 calipers the bulged diameter of the tube and hence causes the tube to be supplied with pressure just suiiicient to bring the bulge to the desired uniform size. It has been found that this pressure may vary considerably. For example, in a lot for which the bulging pressure averages 2,000 pounds, the actual pressure needed to produce a uniform bulge may vary between 1,800 and 2,200 pounds. These Variations are mainly due tol variations in the tube thickness, and also to variations in hardness and other characteristics arising from unavoidable non-uniformities in the tube manufacturing operations. If all of the tubes were bulged at 2,000 pounds as in the prior practice, the finished bellows would show considerable variations both in outside diameter and flexibility. By bulging to a predetermined diameter accordingr to the present invention, the pressure is gauged to the tube characteristics. Thus, for a given lot, the bulge diameter is determined for anormal or average tube. All tubes of the lot are bulged to the same uniform diameter. The pressure required for bulging is maintained during the subsequent contracting operation and since this pressure is' suited to the tube characteristics, it further promotes uniformity of the product.

' Having thus described thel invention, I claim:

wise.

2. Apparatus for forming bellows folds in tubing, comprising means for supporting a tube, a set of die plates encircling the tube and mounted for longitudinal movement, means for bulging the tube between the plates by internal uid pressure, means for measuring the amount of bulge, means controlled by the measuring means upon reaching a predetermined diameter of bulge to retain the bulging pressure within the tube, and means for contracting the tube endwise, and pressure equalizlng means for maintaining in the tube during contraction the pressure reached during the bulging operation.

3. Apparatus for forming bellows folds in tubing comprising means for supporting a tube at its ends, a set of separable die plates to encircle the tube and mounted for longitudinal movement, fluid pressure supply means to initially bulge the tube, means for contracting the tube longitudinally. caliper means for measuring the bulge, valve means controlled by said caliper means for disconnecting the fluid pressure supply means, while maintaining the applied pressure within the tube, and an accumulator for holding the pressure substantially constant during the operation of the contracting means.

4. Apparatus for forming bellows folds in tubing, comprising means for supporting a tube, a set of die plates encircling the tube and mounted for longitudinal movement, means for bulging the tube between the plates by internal fluid pressure, measuring means for the bulged tube, means controlled by the measuring means independently of the bulging pressure to prevent an increase of internal pressure, means for thereafter contracting the tube endwise, and pressurecontrol means for maintaining fluid pressure in the tube during the contracting operation.

5. Apparatus for forming bellows folds in tubing, comprising means for supporting a tube, a set of die plates encircling the tube and mounted for longitudinal movement, means for bulging the tube between the plates by internal fluid pressure, caliper means for measuring the bulged tube, valve means controlled by the caliper means to prevent an increase of internal pressure, means for thereafter contracting the tube endwise, and pressure-control meansv for maintaining fluid pressure in the tube during the contracting operation.

6. Apparatus for forming bellows folds in tubing, comprising means for supporting a tube, a set of die plates encircling the tube and mounted for longitudinal movement, means for bulging the tube between the plates by internal fluid pressure, a measuring means for the bulged tube, means controlled by the measuring means inde- 6 pendently of the bulging pressure to disconnect REFERENCES CITED the uid pressure supply from the tube and thereby to prevent an increase of internal presmr; cilsogtrfferens are of record in the sure, means for thereafter contracting the tube endwise, and pressure-control means for main- 5 UNITED STATES PATENTS taining fluid pressure in the tube during the Number Name Date bulging operation. 2,028,151 Grant Jan. 21, 1936 JOHN E. WOODS. 2,217,799 Giesler Oct. 15, 1940 

